Crude oil refineries typically employ a bank or battery of above ground storage tanks that are used to hold liquids such as crude oil, heavy fuel oil, oil byproducts and the like. Contaminants, solid components, and heavier liquids that are suspended in the stored liquids will typically settle after time to the bottom of a storage tank. These contaminants, solid components, and heavier liquids will create sludge. This sludge can build up over time in an amount sufficient so as to reduce the tank capacity. The sludge buildup may also increase the risk of fire and explosion of retained liquids in the storage tank. Consequently, the sludge that is built up in the tanks comprising the storage tank battery must be periodically removed from the tank.
A number of mechanical devices are utilized for cleaning tanks without the necessity of having a worker enter the tank. Such devices employ nozzles that are positioned at the top or the sides of the tanks to be cleaned. These devices typically employ gimbal mounted nozzles with complicated nozzle guidance mechanisms. When positioned from the top, such devices cause high velocity fluid to be projected down against the tank floor which can cause wear on the tank integrity. When positioned from the sides, such devices fail to sufficiently clean the tank floor which typically has a slight downward slope towards its center. Further, while in use, typical devices have no way of removing spent fluid or the adherent sludge which has been removed. A need exists for a simple, user controlled cleaning device that may be deployed within the interior of an above ground storage tank.
Further, fixed nozzle tank cleaning devices may cause canyons to be formed in the adherent sludge on the tank floor wherein the fluid discharged from the nozzle will no longer remove the adherent sludge. As well, nozzles designed to be rotated within the tank can become locked up by sludge which has been disengaged from the tank floor wherein the nozzle will no longer be allowed to rotate.